Reciprocally folded sheet metal structures



Sept. 20, 1960 s. ETHERIDGE 2,953,110

RECIPROCALLY FOLDED SHEET METAL STRUCTURES Filed Jan. 18, 1955 4 Sheets-Sheet l ttorn e y Sept. 20, 1960 G. ETHERIDGE RECIPROCALLY FOLDED SHEET METAL STRUCTURES 4 Sheets-Sheet 2 Filed Jan. 18, 1955 A ttor'ne y Sept. 20, 1960 G. ETHERIDGE RECIPROCALLY FOLDED SHEET METAL STRUCTURES 4 Sheets-Sheet 3 Filed Jan. 18, 1955 Sept. 20, 1960 G. ETHERIDGE RECIPROCALLY FOLDED SHEET METAL STRUCTURES 4 Sheets-Sheet 4 Filed Jan. 18, 1955 Atlorne Patented Sept. 20, 1960 are RECIPROCALLY FOLDED SHEET METAL STRUCTURES Geoffrey Etheridge, Shotton, Wales, assignor to W. J. Fraser & Co. Limited, Romford, England, a British company Filed Jan. 18, 1955, Ser. No. 482,581 Claims priority, application Great Britain Jan. 22, 1954 2 Claims. (Cl. 113-118) The present invention concerns sheet metal structures, such as heat exchangers for elfecting transfer of heat between two separated bodies of fluid, which include or consist of reciprocally folded sheets.

It has previously been the practice to close or seal the ends of reciprocally folded sheets by attachment thereto of a closure member, for instance a plate insert secured by welding; or alternately by clinching over the end regions so as to form smaller units which can be sealed separately.

An object of the present invention is to provide an improved end closure for such folded sheet metal portions, which enables their ready incorporation in a heat exchange installation.

Another object is to provide a construction which is especially suitable for incorporation in a container adapted to enclose a heated liquid and to be cooled by heat transfer to air or to another liquid surrounding such container which may for example be constituted by the tank of an electrical transformer.

According to the present invention a heat exchanger has two sets of interlaced contrafiow passages, a plurality of mutually parallel wall portions formed by reciprocal folding of a piece of sheet metal transversely between its side edges, the side edge regions of successive pairs of wall portions being set over towards and substantially in contact with one another with the thus contiguous edges sealed together by metal fusion to form a passage end closure, each pair of adjacent wall portions thereby constituting a transversely open heat exchange passage.

The set may be of the order of 50 at a distance from the edge depending upon this angle and upon the desired width of flow passage.

For containers such as transformer or switch-gear tanks in which a liquid is required to dissipate its heat to air surrounding the container, the sets in the sheets, before folding, are arranged in the same direction relative to the plane containing the central or unset portion thereof, that is to say they are both to the same face of the sheet. The result of this is to provide a similar closure of both side edges of each pair of folded wall portions, thereby forming closed pockets.

If, however, a heat exchanger is required for contraflow action between two gases, or for other purposes where symmetrically closed pockets are unsuitable, it may be preferable to impart these sets in opposite directions, whereby after folding the contiguous edges of adjacent wall portions are staggered alternately at opposite side edges of the reciprocally folded portion.

The treatment of the set portions around the 180 or other reciprocal bend will depend upon whether at that bend the set is in an inward or in an outward direction. It inward, the set portion may be bent round sharply by nipping, or a natural sharp bend may be used and the region may be bent around a mandrel of circular or other appropriate shape to avoid excessive curvature or stress. On the other hand, when the flanging is outwardly directed at the bends the excess length of the edge may be shaped to leave the edge portion in the region of the bend lying at to the adjacent contiguous edges.

For transformer casings or other containers for liquids the cover or base of the container to be sealed or joined to the ends of the reciprocal-1y folded sheet metal portion may be bolted to a flange welded to the mutually parallel wall portions along the line of outwardly set bends lying, as described above, at 90 to the contiguous joined edges.

With these and other objects in view which will become apparent in the following detailed description, the present invention will be clearly understood in connection with the. accompanying drawings, in which:

Figure 1 is a perspective view of part of a rectangular metal sheet having set edge regions substantially parallel one to the other and indicating the fold regions;

Fig. 2 is a perspective view of part of a folded metal sheet showing the end closures;

Fig. 3 is a plan corresponding to Fig. 2;

Fig. 4 is a perspective view of a heat exchange installation, the outer casing being broken away to expose its internal structure of mirror image folded metal sheets the set edge regions of which are as shown in Figs. 1 and 2;

Fig. 5 is a detail showing the flanging for sealing the folded metal sheet structure in the casing; and also a wedge-shaped supporting piece;

Fig. 6 is another detail of the flanging showing a connection between it and the outer casing;

Fig. 7 is a detail of an end closure between the mirror image folded metal sheets;

Fig. 8 is a section taken on the line VIIIV]'.II of Fig. 4;

Fig. 9 is a perspective view, with the front end of the casing displaced for clarity, of a heat exchange installation having an internal structure comprising double mirror image folded metal sheets; the set edge regions of which are as shown in Figs. 1 and 2;

Fig. 10 is a perspective view of a heat exchange installation showing a folded metal sheet internal structure the set edge regions of which are to the same face of the sheet;

Fig. 11 is a perspective view of part of the wall structure of a transformer tank including a folded metal sheet wall portion the set edge regions of which are to the same face of the sheet; and

Fig. 12 is a plan view of a tank the walls of which are fitted with one or more heating or cooling elements formed of a folded metal sheet the set edge regions of which are to the same face of the sheet.

Referring now to the drawings, and in particular to Fig. 1, a rectangular metal sheet has an upper surface 10 and an under surface 11. A preliminary set is given to one edge region 12a of the sheet 10, 11 by bending it adjacent and parallel to a first side edge 12 through an acute angle in an upward direction. Similarly a preliminary set is given to an opposite edge region 13a, of the sheet it), 11 by bending it adjacent and parallel to a second side edge 13 through an acute angle in a downward direction. The sheet is then successively folded alternately in opposite directions through approximately about equally spaced fold regions A, B, C, etc., which extend transversely between the edges 12 and 13 of the sheet.

The folding of the flat portion of the sheets may be efiected in a conventional folding machine. The set edges, which are outside the folding tool limits, assume a curved contour at the fold regions which are shaped in the manner described hereunder.

Wall portions 10a, 10b, 10c etc., are thus formed and the side edges 12 or 13 of each alternate pair of adjacent wall portions are substantially contiguous and can now be united by welding, brazing or other suitable process of metal fusion without the use of filler pieces.

At the 180 bends, inwardly directed set portions 14 of edge regions 13:: are bent round sharply by nipping or a natural sharp bend may be used and the region 14 may be bent around a mandrel of circular or other appropriate shape to avoid excessive curvature or stress. The excess lengths of the outwardly directed set portions at the 180 bends, are shaped to leave the edge portion 15 of the edge regions 13a lying at 90 to the adjacent contiguous edges 12 or 13.

The edge portions 15 are thus substantially in one plane thus facilitating the attachment, by welding, of a metal strip such as a flange.

Passages 16a are thus formed having fluid-tight joints at one of their ends and openings at their other ends and these passages 16a are interlaced with passages 16b which have fluid-tight joints at the ends adjacent the open ends of passages 16a and openings at their other ends.

The sets of both edge regions 12 and 13 may, however, be to the same face of the sheet and the resulting passages 16a have fluid-tight joints at both ends, these passages 16a being interlaced with passages 16b which are open at both ends. v

The folded metal structure, hereinafter referred to as a pack, which is described above can be incorporated in a heat exchange installation of thetype diagrammatically illustrated in Figs. 4 to 8 which utilizes two mirror image packs. Two packs 21a and 21b are provided with a continuous flange 23 disposed about the four. peripheral side edges of the combined packs and attached thereto by welding; a dividing wall 22 separates the two packs 21a and 21b along the major part of their length. A return portion of the flange 23 is bolted or otherwise secured to a casing 20 as shown in Fig. 6, gaskets being provided between the casing and the flange as required.

The packs are not attached to the shell except by Way of the flange, in order to allow for expansion along their length. Wedge shaped support members 24 are provided on the casing 20 which project into the transverse openings of the fluid passages, these support members being provided at intervals along the length of the casing. At the free floating end of the packs a connecting means is provided consisting of a sheet metal angle 25 welded to the adjacent edge portions 15 of the two packs as shown in Fig. 7' thereby preventing the intermingling of the two fluid systems; such a metal angle is slightly deformable to ensure sealing between the two packs. The upper ends of both metal sheets are welded at 22a to the dividing wall 22 and the lower ends of both metal sheets are similarly welded thereto at 2217. Alternate passages 16a and 16b are isolated from each other but similar passages 16a and 16b of the two packs 21a and 21b are connected to each other.

Entrance nozzle 26a and exit nozzle 26b are provided for a higher p'r'essure fluid P1. Similarly entrance and exit nozzles 27a and 27b respectively are provided for a lower pressure fluid P2.

The higher pressure fluid P1 enters the pack through nozzle 26a and passes into alternate passages 16b of pack 21b. As these passages are closed at their other extremities and the dividing wall 22 stops short of such extremities the fluid P1 passes into corresponding passages 16b of pack 21a'and from thence out of the casing by way of exit nozzle 26b. The lower pressure fluid P2 enters the casing-at nozzle 27a and passes into alternate passages 16a of pack 21a. These passages 16a are open at the free floating extremities of the pack and the fluid P2' is guided by the back Wall of the casing 20 and is diverted into corresponding passages 16a of pack 21b and from there out of the casing by way of exit nozzle 27b.

Fluid P1 and fluid P2 e'rit'ei and leave the packs substantially at right angles but once inside the fluid flows in their respective interfaced passages are parallel and in opposite directions.

Fig. 9 shows how a double mirror image pack, similar to the mirror image pack shown in Figs. 4 to 8, can be assembled. Mirror image packs'31a and 3111 are separated by dividing wall 32a and packs 31c and 31d are separated by dividing Wall 3217. These two sets of mirror image packs are separated by dividing wall 33. The packs are secured to a casing 30 in the same manner as that described for the embodiment shown in Figs. 4' to 8, the isolation of the alternate fluid passages and also the free floating end closure between the two mirror image packs being performed substantially in the same manner.

The higher pressure fluid P1 enters at nozzle 36a and passes into alternate passages 16b of pack 31a. The free floating extremities of these passages 16b being closed and as the dividing plate 32b is curtailed in this region, the fluid P1 passes into corresponding alternate passages 16b of pack 31d; at the nozzle end of the park 310 the fluid passes through the open ends of passages 16b striking the front wall and being diverted into the corresponding open ends of the alternate passages 16b of pack 31b. A similar operation now takes place for the flow of fluid through the alternate passages 16b of packs 31b and 31a, the fluid P1 finally emerging from the casing through nozzle 36b.

The lower pressure fluid P2 enters the casing 30 at nozzle 37a and passes into alternate passages 16a of pack 31a. The alternate passages 16a are open at the free floating extremities of the packs 31a and 31b and the fluid P2 thus strikes the back wall of the casing 30 and is diverted into corresponding passages 16:! of pack 31b. The dividing wall 33 is supported in' guides 34 on the internal back wall of the casing thus preventing fluid P2 from by-passing alternate passages 16a of pack 31b. The dividing wall 33 is however curtailed at the nozzle end of the casing to allow fluid P2 to pass into alternate passages 16a of pack 31c; these alternate passages 16a of packs 31c and 31d are closed at the nozzle end of the casing and a similar operation now takes place for the flow of fluid through the alternate passages 16a of packs 31c and 31d, the fluid P2 finally emerging from the casing through nozzle 37b. 7

As in the example illustrated in Figs. 4 to 8 the paths of the two fluids P1 and P2 in their respective interlaced passages are always substantially parallel and in opposite directions to each other.

Fig. 10 illustrates diagrammatically a further embodiment of a heat exchange installation in which the pack is formed from a folded metal sheet, the set edge regions of which are to the same face of the sheet, whereby one set of passages have fluid-tight joints at both ends formed by the set edges, these passages being interlaced with passages which are open at both ends.

A container 40 is provided with an entrance nozzle 41a at one end and an exit nozzle (not shown) at the opposite end for a low pressure fluid P2. One side wall of the container has an entrance nozzle 42:: and an exit nozzle 42b for a higher pressure fluid P1.

Low pressure fluid P2 is admitted throughnozzle 41a, passes through the open ended passages and is discharged at the opposite end of the container 40 through the exit nozzle (not shown). The higher pressure fluid P1 is admitted to the closed ended passages by way of nozzle 42a and is discharged at nozzle 42b.v The two fluids are thus admitted to their respective interlaced passages at right angles to each other and the two fluid flows within their respective passages are parallel and in-opposite directions. p A

' Reciprocally folded metal sheets having set edges to the same face of the sheet, forming a plurality of mutually parallel wall portions and having end closures of the type previously described may be used to form part of a transformer wall, the mutually parallel wall portion; projecting outwardly. from the transformer .con-.

tainer 50 as shown diagrammatically in Fig. 11. Partition walls or baflle plates 51 can be welded to some of the interiorly disposed bends of the mutually parallel Wall portions. A flange 54 is welded to both the upper and lower edge portions 52 of ther mutually parallel wall portions, which edge portions, as previously described, are substantially in one plane and are shaped to lie at 90 to the adjacent contiguous edges 53. A cover 55 and a base 56 may now be bolted to the return part of flange 54 as shown. The baflle plates 51 are curtailed both at the top and the bottom leaving a gap in these regions between them and the upper and lower flanges, 54.

Cooling air P4 may enter the open ended flow passages from below and has a straight run through. Hot circulating oil P3 from the transformer container 50 enters the closed ended passages through the gap between the top of the baffle plate 51 and the upper flange 54, as shown by the broken arrow. The oil P3 is cooled by the air P4 and falls down to the bottom of the closed ended passages whilst the air is heated and rises to the top of the open ended passages. The cooled oil P3 reenters the container 50 between the gap formed between the lower edge of the partition wall at the lower flange 54. The directions of entry of the two fluids into their respective interlaced passages are thus at right-angles to each other and the two flows within their respective passages are parallel and in opposite directions.

A folded metal structure of this type may also be used for vessel heating or cooling purposes as shown diagrammatically in Fig. 12. =Mutually parallel wall portions 60, formed in the same manner as described for the embodiment shown in Fig. 11, form part of a vessel wall 61 and are directed toward the interior 62 of such a vessel. Open-ended passages 6012 are interlaced with closedended passages 60a, which latter convey heat from a heating source 63, the walls of these passages thus forming the heating elements.

When used for heating a hot fluid enters the closedended passages 60a horizontally and is conveyed downwardly along these passages. Cold fluid, in the interior 62 of the vessel, due to the transfer of heat through the walls to the passages 6%, moves upwardly along the open-ended passages 60b. The two fluids enter their respective passages at substantially right angles and the two fluid flows in their respective passages are parallel and in opposite directions.

I have disclosed several embodiments of the present invention, it is to be understood that these embodiments are given by example only and not in a limiting sense, the scope of the present invention being determined by the objects and the claims.

I claim:

1. In a method of making a heat exchanger having a front and a rear, from a rectangular metal sheet having a first edge and an opposite second edge, the steps of bending a first edge region of said metal sheet adjacent and parallel to said first edge through an acute angle, bending a second edge region of said metal sheet adjacent and parallel to said second edge through an acute angle, and successively folding said metal sheet alternately in opposite directions through about 180 along substantially equally spaced fold regions extending transversely between said first and second edges into a succession of mutually parallel wall portions spaced apart at a distance, whereby the edges of alternate pairs of said wall portions are brought into abutting relationship to form contiguous edges thereof and to deform simultaneously said contiguous edges into a curved portion at the rear of said heat exchanger, forming said contiguous edges into a substantially straight line at the front of said heat exchanger, the straight line of said contiguous edges of all said wall portions being disposed in one continous straight line along the front of said heat exchanger, and metal fusing said contiguous edges in order to produce a series of substantially fluid-tight parallel heat exchange passages.

2. The method of making a heat exchanger, as set forth in claim 1, wherein said step of forming said contiguous edges into a substantially straight line is performed in a manner to arrange said straight line at an angle of about to said parallel wall portions.

References Cited in the file of this patent UNITED STATES PATENTS 1,886,830 Murray Nov. 8, 1932 2,380,002 Wetherby-Williams July 10, 1945 2,566,310 Burns et a1 Sept. 4, 1951 2,614,517 Peterson Oct. 21, 1952 2,620,169 Gross et al. Dec. 2, 1952 FOREIGN PATENTS 506,891 Great Britain June 6, 1939 

